Characterization of proteome dynamics in oleate reveals a novel peroxisome targeting receptor

To optimally perform the diversity of metabolic functions that occur within peroxisomes, cells must dynamically regulate peroxisome size, number and content in response to cell state and the environment. Except for transcriptional regulation little is known about the mechanisms used to perform this complicated fete. Here we used complementary high content screens to follow changes in most of the yeast, Saccharomyces cerevisiae, proteins during growth in oleate. We found extensive changes in cellular architecture and identified several proteins co-localizing with peroxisomes that have not previously been considered peroxisomal proteins. One of the newly identified peroxisomal proteins, Ymr018w, is a protein with an unknown function that is similar to the yeast and human peroxisomal targeting receptor Pex5. We demonstrate that Ymr018w is a novel peroxisomal targeting receptor that targets a subset of matrix proteins to peroxisomes. We have therefore renamed Ymr018w, Pex9, and suggest that Pex9 is a condition-specific targeting receptor that enables the dynamic rewiring of peroxisomes in response to metabolic needs. Moreover, we suggest that Pex5-like receptors may also exist in vertebrates.